1. Field of the Invention
The present invention relates, in general to a low loss dielectric ceramic composition. The composition is usable for a microwave filter for a global positioning system that is superior in its quality coefficient (Q) value as well as in temperature characteristics of resonant frequency, and in long-term reliability, including high temperature resistance and humidity resistance.
2. Description of the Prior Art
A dielectric filter composition is disclosed in Japanese Patent Publication No. Sho 64-4982 which comprises BaZrSnO. It has a dielectric constant of 37.5 and a Q value of about 6,500. In a view of the dielectric constant and Q value, the dielectric filter composition is useful as a material for a resonator. However since the dielectric filter composition cannot be tightened in its structure, its Q value is lowered and its temperature characteristics become unstable over time at high temperature and high humidity. As a result, the characteristics of the filter deteriorate.
In a paper issued by Shinich Hirano et al. of Japan, a dielectric ceramic composition is reported which shows superior properties, including a dielectric constant of 40, Q value of 5,000, and a resonant frequency temperature coefficient of dielectric constant less than +20 ppm/.degree.C., at 10 GHz. However, the method described requires that fine particles with a diameter of about 0.3 .mu.m be produced in an alkoxide method, and that the baking temperature be 1,600.degree. C. during preparation of the ceramic composition [reference: Shinich Hirano, Takashi Hayashi and Akiyoshi Hattori, "Chemical processing and microwave characteristics of (Zr,Sn)TiO.sub.4 microwave dielectrics." J. Am. Ceram. Soc.; 74 [61]:1320-1324 (1991)].